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Dopamine Transport by the Serotonin Transporter: A Mechanistically Distinct Mode of Substrate Translocation
Journal article   Open access   Peer reviewed

Dopamine Transport by the Serotonin Transporter: A Mechanistically Distinct Mode of Substrate Translocation

Mads Breum Larsen, Mark S Sonders, Ole Valente Mortensen, Gaynor A Larson, Nancy R Zahniser and Susan G Amara
The Journal of neuroscience, v 31(17), pp 6605-6615
27 Apr 2011
PMID: 21525301
url
https://doi.org/10.1523/JNEUROSCI.0576-11.2011View
Published, Version of Record (VoR) Open

Abstract

The serotonin transporter (SERT) is the principal mechanism for terminating serotonin (5-HT) signals in the nervous system and is a site of action for a variety of psychoactive drugs including antidepressants, amphetamines, and cocaine. Here we show that human SERTs (hSERTs) and rat SERTs are capable of robust dopamine (DA) uptake through a process that differs mechanistically from 5-HT transport in several unanticipated ways. DA transport by hSERT has a higher maximum velocity than 5-HT transport, requires significantly higher Na + and Cl − concentrations to sustain transport, is inhibited noncompetitively by 5-HT, and is more sensitive to SERT inhibitors, including selective serotonin reuptake inhibitors. We use a thiol-reactive methane thiosulfonate (MTS) reagent to modify a conformationally sensitive cysteine residue to demonstrate that hSERT spends more time in an outward facing conformation when transporting DA than when transporting 5-HT. Cotransfection of an inactive or an MTS-sensitive SERT with wild-type SERT subunits reveals an absence of cooperative interactions between subunits during DA but not 5-HT transport. To establish the physiological relevance of this mechanism for DA clearance, we show using in vivo high-speed chronoamperometry that SERT has the capacity to clear extracellularly applied DA in the hippocampal CA3 region of anesthetized rats. Together, these observations suggest the possibility that SERT serves as a DA transporter in vivo and highlight the idea that there can be distinct modes of transport of alternative physiological substrates by SERT.

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Web of Science research areas
Neurosciences
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